1. Field of the Description
The present invention relates, in general, to fabrication of three dimensional (3D) objects, and, more particularly, to a 3D printer adapted to provide nearly instantaneous printing via selective curing of a volume or portion of a photo-curing liquid, such as a photopolymer used to provide a fluid print matrix, with the cured volume/portion corresponding to a shape defined by a digital model of a 3D object or a direct, optically transferred, real image of the 3D object.
2. Relevant Background
Presently, 3D printing is a fabrication technology in which objects (or “printed 3D objects”) are created from a digital file, which may be generated from software such as a computer aided design (CAD) program or another 3D modeling program or with a 3D scanner to copy an existing object that provides input to a 3D modeling program. To prepare the digital file for printing, software that is provided on a printer-interfacing computer or running on the 3D printer itself slices or divides the 3D model into hundreds to thousands of horizontal layers. Typically, only the outer wall or “shell” is printed to be solid such that a shell thickness may be defined as part of modifying the 3D model for use in printing. Then, during printing, the shell is printed as a solid element while the interior portions of the 3D object are printed in a honeycomb or another infill design, e.g., to reduce the amount of material that has to be printed to provide the printed 3D object.
When the prepared digital file of the 3D object is uploaded into the 3D printer, the 3D printer creates or prints the object layer-by-layer. The 3D printer reads every slice (or 2D image) from the 3D model and proceeds to create the 3D object by laying down (or printing) successive layers of material until the entire object is created. Each of these layers can be seen as a thinly sliced horizontal cross section of the eventually completed or printed 3D object.
One of the more common 3D printer technologies uses fused deposition modeling (FDM) or, more generally, fused filament fabrication (FFF). FDM printers work by using a plastic filament (e.g., acrylonitrile butadiene styrene (ABS) or polylactic acid (PLA) provided as strands of filament that is 1 to 3 millimeters in diameter) that is unwound from a spool mounted onto the printer housing. The plastic filament is used to supply material to a print head with an extrusion nozzle, e.g., a gear pulls the filament off the spool and into the extrusion nozzle. The extrusion nozzle is adapted to turn its flow on and off. The extrusion nozzle (or an upstream portion of the print head) is heated to melt the plastic filament as it is passed into the extrusion nozzle so that it liquefies. The extrusion nozzle deposits the liquefied material in ultra fine lines, e.g., in lines that are about 0.1 millimeters across.
The extrusion head and its outlet are moved, in both horizontal and vertical directions to complete or print each layer of the 3D model, by a numerically controlled mechanism that is operated by control software running on the 3D printer, e.g., a computer-aided manufacturing (CAM) software package adapted for use with the 3D printer. The extruded melted or liquefied material quickly solidifies to form a layer (and to seal together layers of the 3D object), and the extrusion nozzle is then moved vertically prior to starting the printing of the next layer. This process is repeated until all layers of the 3D object have been printed.
Presently, 3D printing is extremely slow and time consuming. For example, it may take several hours to print a single 3D object even if the 3D object is relatively small (e.g., a 3D object that is only several inches in diameter and four to twelve inches tall). The 3D printing process that uses conventional 3D printers such as an FFF-based 3D printer is limited in its speed by the speed of the mechanism moving the print heads to each new position on a print layer. Hence, there remains a need for 3D printing methods, and 3D printers that implement such methods, that can generate a 3D object with increased speed while retaining or even improving on the quality of the 3D object.
A further problem with existing 3D printing techniques is the need for printing a support structure for any overhanging components of a 3D object. For example, a figurine of a human-like character may have its arms extending outward from its body or torso, and the arms would be cantilevered out from the body or overhang from the adjacent portions of the body. A support structure would have to be included in layers printed below or in advance of the overhanging components or portions of the 3D object to provide material upon which to print the overhanging components. This slows the printing process further as a significant amount of material may have to be printed to provide the support structure. Upon completion of printing, the 3D object requires finishing including removal of the support structure and, in some cases, sanding or polishing of the surfaces from which the support structure was removed to match the finish of adjacent surfaces. These additional steps also increase the production time of the 3D object and typically must be performed manually, which further increases fabrication costs and complexities. Hence, it would be desirable to provide a 3D printing method, and associated 3D printer, that can “print” a 3D object without the need for support structures for overhanging or cantilevered features.